1. Field of the Invention
This invention generally relates to machinery driven by variable speed drives and, more particularly, to systems for heating, ventilation, air-conditioning and refrigeration applications with variable speed components.
2. Description of the Related Art
In machinery that is driven by variable speed drives, there is approximately a five to ten percent penalty in power and efficiency due to losses associated with the operation of the variable speed drive. This efficiency loss or additional power draw is one of the drawbacks that has limited the application of variable speed drives in industrial or other installations. This limitation is especially significant where the need to slow down or speed up the machinery from its normal operating speed is infrequent.
Further, variable speed drive electronics generate heat and are frequently required to be cooled with an external source and/or by diverting a portion of refrigerant circulating through the refrigerant system. Therefore, additional efficiency and power draw penalties are paid to operate variable speed drives within the specified temperature limits. Also, variable speed drives often present a source of unreliability reducing overall system maintenance and uninterrupted service intervals.
Accordingly, there is a need for heating, ventilation, air-conditioning and refrigeration systems with the components driven at variable speeds (or incorporating variable speed drives) with enhanced efficiency of the operation and improved reliability. The method and apparatus of the present invention reduces losses associated with the operation of variable speed drives.
It is an object of the present invention to provide a system for heating, ventilation, air-conditioning and refrigeration applications with an enhanced operational efficiency and improved reliability.
It is a further object of the present invention to provide such a system with an increased service life and maintenance intervals for the components of the variable speed drive system.
It is yet a further object of the present invention to provide a configuration that allows for selective operation of the variable speed drive system.